Compact EM Wave Trapping in Low-Index-Contrast Structures with Al2O3-Based Experimental Validation


Alp İ.

Photonics, vol.13, no.3, pp.1-16, 2026 (SCI-Expanded, Scopus)

  • Publication Type: Article / Article
  • Volume: 13 Issue: 3
  • Publication Date: 2026
  • Doi Number: 10.3390/photonics13030302
  • Journal Name: Photonics
  • Journal Indexes: Scopus, Science Citation Index Expanded (SCI-EXPANDED), Compendex, INSPEC, Directory of Open Access Journals
  • Page Numbers: pp.1-16
  • Gazi University Affiliated: Yes

Abstract

This study presents the design of a compact low-index-contrast structure capable of trapping electromagnetic waves within a highly confined region. The energy storage performance of the geometries was enhanced using a genetic algorithm that employed a binary (present/absent) assignment of insulating cylinders. Time-domain simulations performed with MEEP were experimentally validated using precisely positioned 𝜃-phase alumina rods, resulting in a 13 dB increase in receiver-antenna power within the microwave regime. The measurements showed a correlation exceeding 99% with the computational results over a dielectric constant range of 4.5 to 5.0. A quality factor of Q  =3.6 ×103 was measured at 5.08 GHz in the experiment. Subsequently, machine learning techniques were applied, further increasing the Q value to approximately 104, even within such a small configuration. Furthermore, the proposed structure does not require a complete photonic bandgap; instead, relatively high-Q factors were achieved by suppressing radiation losses through a pattern of low-index dielectric rods.